A distribution system exists which collects and distributes real-time field information, such as, for example, sensor information (earthquakes, rain, etc.) from around the location of a user. In such a distribution system, in many cases, an information provider does not know beforehand who will use the information. Therefore, it is necessary for the user to be able to join the distribution system any time when he wants to refer to data and to be able to change the type of sensor information to be distributed at will.
As a system for referring to such sensor information, a Publication/Subscription communication model is utilized. The Publication/Subscription communication model is a system by which a message is distributed at a timing at which an event occurs in a corresponding topic (for example, “when a window of the home opens”, etc) when a subscription is registered beforehand with respect to the topic (for example, “home”, etc). With this, a transmitter and a receiver do not need to be conscious of who and where the other party is, and the receiver can receive only the messages that he wants. With this Publication/Subscription system, the subscription to a distribution process is available not only for a single user but also for a plurality of users simultaneously.
In addition, in order to inhibit increases in loads and power consumption of communication processing, the information provider is required to integrally deliver, to a certain degree, regularly obtained data.
Thus, when the Publication/Subscription system is used, an intermediary is required between a transmitter (sensor) wishing to transmit a plurality of data simultaneously and a receiver (user) wishing to receive only the necessary data. Therefore, the following technique can be considered.
As a first technique, such a method of integrating all the data in a server of a data center and then individually distributing only the data required for each user can be considered.
Further, as a second technique, multicast distribution by an IP Router as a distribution technique to a plurality of users can also be considered. The multicast distribution is a process of relaying in units of packets. When the multicast distribution is used, by distributing the data output from the sensor to all users as they are, the data can be collected and distributed by being dispersedly processed at plural nodes, thereby shortening a delay. In addition, a technique related to the above mentioned multicast distribution includes, for example, a technique related to MPLS (Multi-Protocol Label Switching).
Further, as a third technique, the following can be considered. A terminal receives streaming data from a stream server and requests to view the program to be viewed related to the streaming data. The stream server, before transmitting the streaming data to the terminal which requested viewing, caches common information of said program to be viewed to the common information data base and receives the viewing request for the same program to be viewed from other terminals. Then, the stream server, after transmitting the common information of the common information data base to said other terminals, also transmits the streaming data actually distributed from the stream server to the other terminals as well in addition to the terminal under transmission.
Further, as a fourth technique, the following can be considered. A management server generates instructing information for preparing complex content on the basis of the content of the complex content to be prepared. A piece of intermediary equipment instructs a content server to eject a content part required for preparing the complex content in accordance with the instructing information. Each content server, by corresponding to the content part instructed to be ejected, acquires the complex contents elements whose encoding format is converted for a mobile terminal and responds to the intermediary equipment. The intermediary equipment combines, in chronologic order, the complex contents elements that the contents server responded with on the basis of the instructing information from the management server and prepares them as complex contents for a mobile terminal. The management server distributes the prepared complex contents to the mobile terminal.
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Patent Document 2: Japanese Laid-open Patent Publication No. 2002-290952
Patent Document 3: Japanese Laid-open Patent Publication No. 2005-20588
Patent Document 4: Japanese National Publication of International Patent Application No. 2005-506744
Patent Document 5: Japanese Laid-open Patent Publication No. 2007-234014